diff --git a/.github/actions/get-next-package-version.js b/.github/actions/get-next-package-version.js
deleted file mode 100644
index 16e22f7880..0000000000
--- a/.github/actions/get-next-package-version.js
+++ /dev/null
@@ -1,117 +0,0 @@
-#!/usr/bin/env node
-
-// This script is used in GitHub Actions to get the next version based on the current package.json version.
-// It supports three types of versioning: nightly, hotfix, and monthly.
-
-const { parseArgs } = require('node:util');
-const fs = require('node:fs');
-
-const args = process.argv;
-
-const options = {
-  'package-json': {
-    type: 'string',
-    short: 'p',
-  },
-  type: {
-    type: 'string', // nightly, hotfix, monthly, auto
-    short: 't',
-  },
-  update: {
-    type: 'boolean',
-    short: 'u',
-    default: false,
-  },
-};
-
-const { values } = parseArgs({
-  args,
-  options,
-  allowPositionals: true,
-});
-
-if (!values['package-json']) {
-  console.error(
-    'Please specify the path to package.json using --package-json or -p option.',
-  );
-  process.exit(1);
-}
-
-try {
-  const packageJsonPath = values['package-json'];
-
-  // Read and parse package.json
-  const packageJson = JSON.parse(fs.readFileSync(packageJsonPath, 'utf8'));
-  const currentVersion = packageJson.version;
-
-  // Parse year and month from version (e.g. 25.5.1 -> year=2025, month=5)
-  const versionParts = currentVersion.split('.');
-  const versionYear = parseInt(versionParts[0]);
-  const versionMonth = parseInt(versionParts[1]);
-  const versionHotfix = parseInt(versionParts[2]);
-
-  // Create date and add 1 month
-  const versionDate = new Date(2000 + versionYear, versionMonth - 1, 1); // month is 0-indexed
-  const nextVersionMonthDate = new Date(
-    versionDate.getFullYear(),
-    versionDate.getMonth() + 1,
-    1,
-  );
-
-  // Format back to YY.M format
-  const nextVersionYear = nextVersionMonthDate
-    .getFullYear()
-    .toString()
-    .slice(nextVersionMonthDate.getFullYear() < 2100 ? -2 : -3);
-  const nextVersionMonth = nextVersionMonthDate.getMonth() + 1; // Convert back to 1-indexed
-
-  // Get current date string
-  const currentDate = new Date();
-  const currentDateString = currentDate
-    .toISOString()
-    .split('T')[0]
-    .replaceAll('-', '');
-
-  if (values.type === 'auto') {
-    if (currentDate.getDate() <= 25) {
-      values.type = 'hotfix';
-    } else {
-      values.type = 'monthly';
-    }
-  }
-
-  let newVersion;
-  switch (values.type) {
-    case 'nightly': {
-      newVersion = `${nextVersionYear}.${nextVersionMonth}.0-nightly.${currentDateString}`;
-      break;
-    }
-    case 'hotfix': {
-      newVersion = `${versionYear}.${versionMonth}.${versionHotfix + 1}`;
-      break;
-    }
-    case 'monthly': {
-      newVersion = `${nextVersionYear}.${nextVersionMonth}.0`;
-      break;
-    }
-    default:
-      console.error(
-        'Invalid type specified. Use "auto", "nightly", "hotfix", or "monthly".',
-      );
-      process.exit(1);
-  }
-
-  process.stdout.write(newVersion); // return the new version to stdout
-
-  if (values.update) {
-    packageJson.version = newVersion;
-    fs.writeFileSync(
-      packageJsonPath,
-      JSON.stringify(packageJson, null, 2) + '\n',
-      'utf8',
-    );
-  }
-} catch (error) {
-  console.error('Error:', error.message);
-  process.exit(1);
-}
diff --git a/.github/workflows/generate-release-pr.yml b/.github/workflows/generate-release-pr.yml
index 61fb5e9191..89d0a147b1 100644
--- a/.github/workflows/generate-release-pr.yml
+++ b/.github/workflows/generate-release-pr.yml
@@ -37,7 +37,7 @@ jobs:
             if [[ -n "${{ github.event.inputs.version }}" ]]; then
               version="${{ github.event.inputs.version }}"
             else
-              version=$(node ./.github/actions/get-next-package-version.js \
+              version=$(node ./packages/ci-actions/bin/get-next-package-version.js \
                 --package-json "./packages/$pkg/package.json" \
                 --type auto \
                 --update)
diff --git a/.github/workflows/publish-nightly-npm-packages.yml b/.github/workflows/publish-nightly-npm-packages.yml
index 9c7b47c1d4..33b514f6a3 100644
--- a/.github/workflows/publish-nightly-npm-packages.yml
+++ b/.github/workflows/publish-nightly-npm-packages.yml
@@ -20,9 +20,9 @@ jobs:
       - name: Update package versions
         run: |
           # Get new nightly versions
-          NEW_WEB_VERSION=$(node ./.github/actions/get-next-package-version.js --package-json ./packages/desktop-client/package.json --type nightly)
-          NEW_SYNC_VERSION=$(node ./.github/actions/get-next-package-version.js --package-json ./packages/sync-server/package.json --type nightly)
-          NEW_API_VERSION=$(node ./.github/actions/get-next-package-version.js --package-json ./packages/api/package.json --type nightly)
+          NEW_WEB_VERSION=$(node ./packages/ci-actions/bin/get-next-package-version.js --package-json ./packages/desktop-client/package.json --type nightly)
+          NEW_SYNC_VERSION=$(node ./packages/ci-actions/bin/get-next-package-version.js --package-json ./packages/sync-server/package.json --type nightly)
+          NEW_API_VERSION=$(node ./packages/ci-actions/bin/get-next-package-version.js --package-json ./packages/api/package.json --type nightly)
 
           # Set package versions
           npm version $NEW_WEB_VERSION --no-git-tag-version --workspace=@actual-app/web --no-workspaces-update
diff --git a/packages/ci-actions/bin/get-next-package-version.js b/packages/ci-actions/bin/get-next-package-version.js
new file mode 100755
index 0000000000..e2e5436dc7
--- /dev/null
+++ b/packages/ci-actions/bin/get-next-package-version.js
@@ -0,0 +1,73 @@
+#!/usr/bin/env node
+
+// This script is used in GitHub Actions to get the next version based on the current package.json version.
+// It supports three types of versioning: nightly, hotfix, and monthly.
+
+import fs from 'node:fs';
+import { parseArgs } from 'node:util';
+
+// eslint-disable-next-line import/extensions
+import { getNextVersion } from '../src/versions/get-next-package-version.js';
+
+const args = process.argv;
+
+const options = {
+  'package-json': {
+    type: 'string',
+    short: 'p',
+  },
+  type: {
+    type: 'string', // nightly, hotfix, monthly, auto
+    short: 't',
+  },
+  update: {
+    type: 'boolean',
+    short: 'u',
+    default: false,
+  },
+};
+
+const { values } = parseArgs({
+  args,
+  options,
+  allowPositionals: true,
+});
+
+if (!values['package-json']) {
+  console.error(
+    'Please specify the path to package.json using --package-json or -p option.',
+  );
+  process.exit(1);
+}
+
+try {
+  const packageJsonPath = values['package-json'];
+  const packageJson = JSON.parse(fs.readFileSync(packageJsonPath, 'utf8'));
+  const currentVersion = packageJson.version;
+
+  let newVersion;
+  try {
+    newVersion = getNextVersion({
+      currentVersion,
+      type: values.type,
+      currentDate: new Date(),
+    });
+  } catch (e) {
+    console.error(e.message);
+    process.exit(1);
+  }
+
+  process.stdout.write(newVersion);
+
+  if (values.update) {
+    packageJson.version = newVersion;
+    fs.writeFileSync(
+      packageJsonPath,
+      JSON.stringify(packageJson, null, 2) + '\n',
+      'utf8',
+    );
+  }
+} catch (error) {
+  console.error('Error:', error.message);
+  process.exit(1);
+}
diff --git a/packages/ci-actions/package.json b/packages/ci-actions/package.json
new file mode 100644
index 0000000000..48c5e68a2b
--- /dev/null
+++ b/packages/ci-actions/package.json
@@ -0,0 +1,11 @@
+{
+  "name": "@actual-app/ci-actions",
+  "private": true,
+  "type": "module",
+  "devDependencies": {
+    "vitest": "^3.2.4"
+  },
+  "scripts": {
+    "test": "vitest"
+  }
+}
diff --git a/packages/ci-actions/src/versions/get-next-package-version.js b/packages/ci-actions/src/versions/get-next-package-version.js
new file mode 100644
index 0000000000..eb6dfc27a4
--- /dev/null
+++ b/packages/ci-actions/src/versions/get-next-package-version.js
@@ -0,0 +1,72 @@
+function parseVersion(version) {
+  const [y, m, p] = version.split('.');
+  return {
+    versionYear: parseInt(y, 10),
+    versionMonth: parseInt(m, 10),
+    versionHotfix: parseInt(p, 10),
+  };
+}
+
+function computeNextMonth(versionYear, versionMonth) {
+  // Create date and add 1 month
+  const versionDate = new Date(2000 + versionYear, versionMonth - 1, 1); // month is 0-indexed
+  const nextVersionMonthDate = new Date(
+    versionDate.getFullYear(),
+    versionDate.getMonth() + 1,
+    1,
+  );
+
+  // Format back to YY.M format
+  const fullYear = nextVersionMonthDate.getFullYear();
+  const nextVersionYear = fullYear.toString().slice(fullYear < 2100 ? -2 : -3);
+  const nextVersionMonth = nextVersionMonthDate.getMonth() + 1; // Convert back to 1-indexed
+  return { nextVersionYear, nextVersionMonth };
+}
+
+// Determine logical type from 'auto' based on the current date and version
+function resolveType(type, currentDate, versionYear, versionMonth) {
+  if (type !== 'auto') return type;
+  const inPatchMonth =
+    currentDate.getFullYear() === 2000 + versionYear &&
+    currentDate.getMonth() + 1 === versionMonth;
+  if (inPatchMonth && currentDate.getDate() <= 25) return 'hotfix';
+  return 'monthly';
+}
+
+export function getNextVersion({
+  currentVersion,
+  type,
+  currentDate = new Date(),
+}) {
+  const { versionYear, versionMonth, versionHotfix } =
+    parseVersion(currentVersion);
+  const { nextVersionYear, nextVersionMonth } = computeNextMonth(
+    versionYear,
+    versionMonth,
+  );
+  const resolvedType = resolveType(
+    type,
+    currentDate,
+    versionYear,
+    versionMonth,
+  );
+
+  // Format date stamp once for nightly
+  const currentDateString = currentDate
+    .toISOString()
+    .split('T')[0]
+    .replaceAll('-', '');
+
+  switch (resolvedType) {
+    case 'nightly':
+      return `${nextVersionYear}.${nextVersionMonth}.0-nightly.${currentDateString}`;
+    case 'hotfix':
+      return `${versionYear}.${versionMonth}.${versionHotfix + 1}`;
+    case 'monthly':
+      return `${nextVersionYear}.${nextVersionMonth}.0`;
+    default:
+      throw new Error(
+        'Invalid type specified. Use “auto”, “nightly”, “hotfix”, or “monthly”.',
+      );
+  }
+}
diff --git a/packages/ci-actions/src/versions/get-next-package-version.test.js b/packages/ci-actions/src/versions/get-next-package-version.test.js
new file mode 100644
index 0000000000..031019e298
--- /dev/null
+++ b/packages/ci-actions/src/versions/get-next-package-version.test.js
@@ -0,0 +1,85 @@
+import { describe, it, expect } from 'vitest';
+
+import { getNextVersion } from './get-next-package-version';
+
+describe('getNextVersion (lib)', () => {
+  it('hotfix increments patch', () => {
+    expect(
+      getNextVersion({
+        currentVersion: '25.8.1',
+        type: 'hotfix',
+        currentDate: new Date('2025-08-10'),
+      }),
+    ).toBe('25.8.2');
+  });
+
+  it('monthly advances month same year', () => {
+    expect(
+      getNextVersion({
+        currentVersion: '25.8.3',
+        type: 'monthly',
+        currentDate: new Date('2025-08-15'),
+      }),
+    ).toBe('25.9.0');
+  });
+
+  it('monthly wraps year December -> January', () => {
+    expect(
+      getNextVersion({
+        currentVersion: '25.12.3',
+        type: 'monthly',
+        currentDate: new Date('2025-12-05'),
+      }),
+    ).toBe('26.1.0');
+  });
+
+  it('nightly format with date stamp', () => {
+    expect(
+      getNextVersion({
+        currentVersion: '25.8.1',
+        type: 'nightly',
+        currentDate: new Date('2025-08-22'),
+      }),
+    ).toBe('25.9.0-nightly.20250822');
+  });
+
+  it('auto before 25th -> hotfix', () => {
+    expect(
+      getNextVersion({
+        currentVersion: '25.8.4',
+        type: 'auto',
+        currentDate: new Date('2025-08-20'),
+      }),
+    ).toBe('25.8.5');
+  });
+
+  it('auto after 25th (same month) -> monthly', () => {
+    expect(
+      getNextVersion({
+        currentVersion: '25.8.4',
+        type: 'auto',
+        currentDate: new Date('2025-08-27'),
+      }),
+    ).toBe('25.9.0');
+  });
+
+  it('auto after 25th (next month) -> monthly', () => {
+    expect(
+      getNextVersion({
+        currentVersion: '25.8.4',
+        type: 'auto',
+        currentDate: new Date('2025-09-02'),
+      }),
+    ).toBe('25.9.0');
+  });
+
+  it('invalid type throws', () => {
+    expect(() =>
+      getNextVersion({
+        currentVersion: '25.8.4',
+        type: 'unknown',
+        currentDate: new Date('2025-08-10'),
+      }),
+    ).toThrow(/Invalid type/);
+  });
+});
diff --git a/packages/ci-actions/vitest.config.mts b/packages/ci-actions/vitest.config.mts
new file mode 100644
index 0000000000..81a9c30fa1
--- /dev/null
+++ b/packages/ci-actions/vitest.config.mts
@@ -0,0 +1,9 @@
+import { defineConfig } from 'vitest/config';
+
+export default defineConfig({
+  test: {
+    globals: true,
+    include: ['src/**/*.test.(js|jsx|ts|tsx)'],
+    environment: 'node',
+  },
+});
diff --git a/upcoming-release-notes/5662.md b/upcoming-release-notes/5662.md
new file mode 100644
index 0000000000..2f41839953
--- /dev/null
+++ b/upcoming-release-notes/5662.md
@@ -0,0 +1,6 @@
+---
+category: Maintenance
+authors: [jfdoming]
+---
+
+Fix version bump logic to work if the month has rolled over
diff --git a/yarn.lock b/yarn.lock
index 9eca68198b..a7bf6a07bb 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -34,6 +34,14 @@ __metadata:
   languageName: unknown
   linkType: soft
 
+"@actual-app/ci-actions@workspace:packages/ci-actions":
+  version: 0.0.0-use.local
+  resolution: "@actual-app/ci-actions@workspace:packages/ci-actions"
+  dependencies:
+    vitest: "npm:^3.2.4"
+  languageName: unknown
+  linkType: soft
+
 "@actual-app/components@workspace:*, @actual-app/components@workspace:packages/component-library":
   version: 0.0.0-use.local
   resolution: "@actual-app/components@workspace:packages/component-library"